基于遥感指数的干旱内陆河流域土地生态敏感性时空演变特征——以石羊河流域武威市为例

Spatiotemporal evolution of land ecological sensitivity in arid inland river basin based on remote sensing index:A case of Wuwei City in Shiyang River Basin

为评价石羊河流域治理工程实施的成效,本文选用流域重点区域——武威市作为研究区,在综合考虑武威市土地实际状况的基础上,利用遥感数据,借助GIS和RS技术,选取土壤侵蚀、土壤荒漠化、土壤含水量和土壤盐渍化4个指数,构建武威市土地生态敏感性评价体系,运用主成分分析法综合各指数,得到1995、2000、2005、2010、2015和2018年的土地生态敏感性空间分布数据,并对其时空演变规律进行了探讨。结果表明:(1)武威市土地生态敏感性整体呈现西南低、东北高、渐进式的分布格局,随时间推移,部分中、强度敏感性土地转变为轻、微度敏感性土地,总体上敏感性有所降低;(2)武威市50%以上的土地其敏感性变化频次处于较低水平,未发生大规模的高频转化现象,不同地物类型之间频次差异明显,而内部分布相对集中;(3)武威市90%以上的土地变化趋势为稳定不变或波动变化模式,局部地区为波动下降或波动上升模式,整体而言土地恢复面积大于退化面积,土地生态环境趋于良好;(4)武威市土地生态敏感性波动范围在0~1.8,处于不稳定状态,经历了1995—2005年先恶化、2005—2018年逐步恢复的过程,表明石羊河流域治理工程实施后,生态环境得到改善,生态治理效果较显著。

We evaluated the effectiveness of the Shiyang River Basin governance project,with Wuwei,a key area of the river basin,as the research area.Based on the remote sensing data and analysis of GIS,with four indices including soil erosion,soil desertification,soil water content and soil salinization,the evaluation system of land ecological sensitivity in Wuwei was established.With the principal component analysis,we analyzed spatial distribution of land ecological sensitivity in 1995,2000,2005,2010,2015 and 2018 and the temporal and spatial evolution patterns.Results showed that:(1)land ecological sensitivity was generally lower in the southwest and higher in the northeast,with a gradual distribution pattern.Some moderately/intensively sensitive land had been transformed into mildly/slightly sensitive land,resulting in a reduction of the overall sensitivity.(2)Over 50%of the land had a relatively low frequency of sensitivity changes,without large-scale high-frequency conversion.The frequency of different land types varied significantly,while the internal distribution was relatively concentrated.(3)More than 90%of land ecological sensitivity change was stable or fluctuating,and in some areas,the pattern was in fluctuating declining or rising.Overall,the restored land area was larger than the degraded area and the land ecological environment was tending good.(4)The fluctuation range of land ecological sensitivity was from 0 to 1.8,which was unstable.A deteriorating process was recorded from 1995 to 2005 and gradually recovering process from 2005 to 2018,indicating that ecological environment in the Shiyang River Basin had been improved and that the outputs of ecological management were remarkable.